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R32 Respirology
Sleep-Related Breathing Disorders Toronto Notes 2019 Sleep-Related Breathing Disorders
Hypoventilation Syndromes
• primaryalveolarhypoventilation:idiopathic
• obesity-hypoventilationsyndrome(Pickwickiansyndrome) • respiratoryneuromusculardisorders
Sleep Apnea
Definition
• episodicdecreasesinairflowduringsleep
• quantitativelymeasuredbytheApnea/HypopneaIndex(AHI)=#ofapneicandhypopneiceventsper
hour of sleep
• sleepapneagenerallyacceptedtobepresentifAHI>15
Classification
• obstructive(OSA)
■ caused by transient, episodic obstruction of the upper airway ■ absent or reduced airflow despite persistent respiratory effort
• central(CSA)(seeNeurology,N47)
■ can be hypercapneic CSA caused by transient, episodic decreases in CNS drive to breathe or
nonhypercapnic where the drive to breathe is increased ■ no airflow because no respiratory effort
• Cheyne-StokesRespiration:aformofCSAinwhichcentralapneasalternatewithhyperpneasto produce a crescendo-decrescendo pattern of tidal volume; seen in severe LV dysfunction, brain injury, and other settings (see Figure 2)
• mixed(MSA)
■ features of both OSA and CSA
■ loss of hypoxic and hypercapnic drives to breathe secondary to “resuscitative breathing”:
overcompensatory hyperventilation upon awakening from OSA induced hypoxia
Risk Factors
• forOSA:obesity,upperairwayabnormality,neuromusculardisease,hypothyroidism,alcohol/sedative use, nasal congestion, sleep deprivation, enlarged tonsils, crowded oropharynx
• forCSA:LVfailure,brainstemlesions,stroke,braintumours,encephalitis,encephalopathy,obesity (hypoventilation), neuromuscular disease, myxedema, high altitude, narcotics
Signs and Symptoms
• obtainhistoryfromspouse/partner
• secondary to repeated arousals and fragmentation of sleep: nocturnal gasping/choking, daytime
somnolence, personality and cognitive changes, snoring
• secondary to hypoxemia and hypercapnia: morning headache, polycythemia, pulmonary/systemic
HTN, cor pulmonale/CHF, nocturnal angina, arrhythmias
• atypicalpresentationforOSAisamiddle-agedobesemalewhosnores
Investigations
• sleepstudy(polysomnography)
• evaluates sleep stages, (EEG, EOG, EMG), airflow, ribcage movement, arousals, ECG, SaO2, limb
movements, snoring, body position • indications
■ excessive daytime sleepiness
■ unexplained pulmonary HTN or polycythemia
■ daytime hypercapnia
■ titration of optimal nasal CPAP or BiPAP
■ assessment of objective response to other interventions (e.g. oral appliances for sleep apnea,
positional therapy)
Treatment
• modifiablefactors:weightloss,decreasedalcohol/sedatives,nasaldecongestion,treatmentofunderlying medical conditions
• OSAorMSA:nasalCPAP,posturaltherapy(e.g.nosupinesleeping),dentalappliance
• CSA or hypoventilation syndromes: nasal BiPAP/CPAP, respiratory stimulants (e.g. acetazolamide,
theophylline, progesterone), adaptive servoventilation (e.g. progesterone) in select cases • tracheostomy rarely required and should be used as last resort for OSA
Complications
• depression,weightgain,decreasedqualityoflife,workplaceandvehicularaccidents,cardiac complications (e.g. HTN), reduced work/social function
• associatedwithhigherpotentialriskofCVScomplicationsincludingheartattacks,strokes,arrhythmias and heart failure
Normal Respiratory Changes during Sleep
• Tidal volume decreases
• Arterial CO2 increases (due to decreased
minute ventilation)
• Pharyngeal dilator muscles relax causing
increased upper airway resistance
Apnea: absence of breathing for ≥10 s Hypopnea: excessive decrease in rate or depth of breathing (>50% reduction in ventilation for >10 sec)
Hyperpnea: excessive increase in rate or depth of breathing
Continuous Positive Airways Pressure for Obstructive Sleep Apnea
Cochrane DB Syst Rev 2006;CD001106
Study: Pooled analysis of 36 RCTs (n=1,718) comparing nocturnal CPAP with an inactive control or oral appliances in adults with OSA. Conclusions: The use of CPAP showed significant improvements in objective and subjective measures including cognitive function, sleepiness, measures of quality of life, and a lower average systolic and diastolic blood pressure. People who responded equally well to CPAP and oral appliances expressed a strong preference for oral appliances; however, participants on oral appliances were more likely to withdraw from therapy.
CPAP has been shown to reduce cardiovascular risk and cardiovascular related deaths in patients with obstructive sleep apnea